Here is a sentence from The Lion, the Witch and the Wardrobe:
He had eaten his share of the dinner, but he hadn't really enjoyed it because he was thinking all the time about Turkish Delight—and there's nothing that spoils the taste of good ordinary food half so much as the memory of bad magic food.
I don't quite understand what the half adds to the meaning of the whole expression. Is it being used as an intensifier of sorts, and, if paraphrased, could that part of the sentence be something like:
There's nothing at all that spoils the taste of good ordinary food
halfso much as the memory of bad magic food.